Field of the Invention
The present invention relates to polypeptide having cellulolytic enhancing activity variants, polynucleotides encoding the variants, methods of producing the variants, and methods of using the variants.
Description of the Related Art
Cellulose is a polymer of the simple sugar glucose covalently linked by beta-1,4-bonds. Many microorganisms produce enzymes that hydrolyze beta-linked glucans. These enzymes include endoglucanases, cellobiohydrolases, and beta-glucosidases. Endoglucanases digest the cellulose polymer at random locations, opening it to attack by cellobiohydrolases. Cellobiohydrolases sequentially release molecules of cellobiose from the ends of the cellulose polymer. Cellobiose is a water-soluble beta-1,4-linked dimer of glucose. Beta-glucosidases hydrolyze cellobiose to glucose.
The conversion of lignocellulosic feedstocks into ethanol has the advantages of the ready availability of large amounts of feedstock, the desirability of avoiding burning or land filling the materials, and the cleanliness of the ethanol fuel. Wood, agricultural residues, herbaceous crops, and municipal solid wastes have been considered as feedstocks for ethanol production. These materials primarily consist of cellulose, hemicellulose, and lignin. Once the lignocellulose is converted to fermentable sugars, e.g., glucose, the fermentable sugars are easily fermented by yeast into ethanol.
WO 2005/074647, WO 2008/148131, WO 2011/035027 disclose isolated GH61 polypeptides having cellulolytic enhancing activity and the polynucleotides thereof from Thielavia terrestris. WO 2005/074656 and WO 2010/065830 disclose isolated GH61 polypeptides having cellulolytic enhancing activity and the polynucleotides thereof from Thermoascus aurantiacus. WO 2007/089290 discloses an isolated GH61 polypeptide having cellulolytic enhancing activity and the polynucleotide thereof from Trichoderma reesei. WO 2009/085935, WO 2009/085859, WO 2009/085864, and WO 2009/085868 disclose isolated GH61 polypeptides having cellulolytic enhancing activity and the polynucleotides thereof from Myceliophthora thermophila. WO 2010/138754 discloses isolated GH61 polypeptides having cellulolytic enhancing activity and the polynucleotides thereof from Aspergillus fumigatus. WO 2011/005867 discloses isolated GH61 polypeptides having cellulolytic enhancing activity and the polynucleotides thereof from Penicillium pinophilum. WO 2011/039319 discloses isolated GH61 polypeptides having cellulolytic enhancing activity and the polynucleotides thereof from Thermoascus sp. WO 2011/041397 discloses isolated GH61 polypeptides having cellulolytic enhancing activity and the polynucleotides thereof from Penicillium sp. WO 2011/041504 discloses isolated GH61 polypeptides having cellulolytic enhancing activity and the polynucleotides thereof from Thermoascus crustaceous. WO 2008/151043 discloses methods of increasing the activity of a GH61 polypeptide having cellulolytic enhancing activity by adding a soluble activating divalent metal cation to a composition comprising the polypeptide.
It would be advantageous in the art to improve the ability of polypeptides having cellulolytic enhancing activity to enhance enzymatic degradation of lignocellulosic feedstocks.
The present invention provides variants of a polypeptide having cellulolytic enhancing activity with improved properties.